This invention relates to ceramic materials and more particularly to ceramic materials based on metal borides.
Early studies on diboride materials had focused primarily on group VI metal diborides. Ceramics based on zirconium diboride (ZrB.sub.2) and hafnium diboride (HfB.sub.2) were developed through the 1960s by the U.S. Air Force for advanced hypersonic vehicle leading edges. While those materials are useful, it was desirable to improve their physical properties.
In U.S. Pat. No. 5,571,759 filed on Oct. 31, 1995 (parent of the present application), ceramic materials based on solid solutions of chromium diboride (CrB.sub.2) and niobium diboride (NbB2) are disclosed which have excellent hardness and resistance to oxidation. Unfortunately, these materials have low strengths in the compositions having the highest hardness and highest resistance to oxidation. It would be desirable to produce materials having greater strength but which retain the excellent hardness and resistance to oxidation of the CrB.sub.2 --NbB.sub.2 ceramic materials.